Lancing device and method of sample collection

ABSTRACT

A lancing device and method for self-collecting a sample of body fluid by penetrating a body tissue at a sampling site. The invention includes a housing geometry configured for ease of use at different sampling sites on the body, even by persons having reduced dexterity and/or poor vision. Depth of penetration is selectively controlled by adjusting the stroke range of a spring-driven lancet carrier. A pressure applicator is included for stimulating flow of the body fluid. A transparent portion permits observation of the sampling site.

FIELD OF THE INVENTION

[0001] The present invention relates generally to devices and methodsfor use in medical sampling and testing, and more particularly to alancing device and a method for penetrating body tissue to obtain asample of body fluid.

BACKGROUND OF THE INVENTION

[0002] Samples of blood, interstitial fluid, or other body fluids arecommonly required for various medical purposes. For example, manydiabetics must periodically monitor their blood glucose level todetermine when an insulin injection is needed. Self-testing systems areavailable to enable a person to obtain a sample of his or her own blood,typically by penetrating the skin, and to subject the harvested bloodsample to analysis of the blood glucose level. Often, a lancing deviceis used to penetrate the skin to obtain the required sample of blood.For example, U.S. Pat. Nos. 5,954,738; 5,879,311; 5,857,983; and5,318,584 disclose particular forms of body fluid sampling devices.

[0003] In order to encourage compliance in regular usage, it is highlydesirable that the use of a lancing device be as painless as possible toa subject obtaining a blood sample. Because the fingertips are rich incapillaries, a number of lancing devices have been designed for samplecollection from this region. Nerve density is high in the fingertips,however, and significant pain often results from fingertip sampling.Moreover, repeated sampling can adversely result in callous formation onthe fingertips. Accordingly, testing procedures have been developedallowing sampling at other sites on the body, such as the earlobe orforearm. By appropriate selection of the sampling site, the lancetgeometry and the depth of penetration, the required sample size isobtained. According to present and developing sampling methods, samplesizes of about 8-10 microliters (μL), and in some instances about 2-3microliters (μL), and possibly as little as about 400 nanoliters (nL)are sufficient for blood glucose analysis. It is anticipated thatcontinuing developments in the field will progressively reduce therequired sample size. In order to minimize pain and speed healing, it isdesirable to minimize the size of the opening in the skin that isrequired to obtain a sample of the requisite size. To further reducepain, it is also desirable that the lancing operation incorporate aquick penetration and retraction stroke, wherein the piercing instrumentpenetrates the skin and is quickly retracted along a substantiallylinear path.

[0004] It has also been found advantageous to provide a lancing devicethat is configured for ease of manipulation and use at differentsampling sites. This is of particular importance with lancing devicesintended for use by diabetics, as many diabetics suffer from pooreyesight and neuropathy, often resulting in reduced manual dexterity.Many previously known lancing devices have been found particularlydifficult for such users to manipulate in carrying out certain samplingmethods. For example, pen-shaped lancing devices are often too narrowfor some users to grasp easily, and their cylindrical shape may renderthem difficult for some users to hold without unintentional twisting ofthe barrel of the device. Also, because such devices are typicallyrelatively long compared to their width (or diameter) it is difficultfor some users to apply sufficient pressure to maintain the device in astable manner against the user's forearm during sampling. Other lancingdevices incorporate non-symmetric or non-rectangular housings and/orhousings with gripping surfaces or sample site contacting surfaces thatare offset at oblique angles from the stroke axis of their lancets. Suchdevices are generally adapted for fingertip sampling, but are notwell-suited for sampling at a site on the forearm. In particular, due totheir angular offset, many users find it difficult to press theselancing devices against the forearm while maintaining the device in anorientation for lancing perpendicularly to the skin.

[0005] A number of previously known lancing devices enable penetrationof the skin to a single, predetermined depth. Because of differencesbetween individual users, such devices may generate a sample size largeror smaller than necessary. Accordingly it is desirable to provide alancing device that enables easy adjustment of the depth of penetration,and that provides a reliable and accurate depth stop for providing adesired depth of penetration.

[0006] For purposes of commercial appeal to consumers, it has been founddesirable to provide a lancing device that is compatible with standard,commercially available, disposable lancets. It is preferable that astandard lancet be readily mountable to a lancing device prior to use,and that the lancet also be readily and safely removable from thelancing device for deposit in a sharps container or other disposalcanister. Particular forms of previously known lancing devices haveincorporated an eject feature that permits a lancet to be “launched”from the device, potentially resulting in injury. Other known devicesrequire the user to grasp the used lancet for removal, therebypresenting a risk of needle sticks. Accordingly, it would be preferableto provide a lancing device enabling safer and more controlled releaseof a lancet.

[0007] Certain previously known sampling devices provide for theapplication of pressure to tissue surrounding an incision to stimulatethe formation of a drop of sampled fluid. The configuration ofpreviously known stimulator members has been found to provide less thanoptimal sampling rates, to result in undesirable levels of userdiscomfort, and to result in bruising or marking of the skin withpressure indentations. In addition, it is often difficult to monitor thesample size produced during use of such previously known devices.Accordingly, it would be preferable to provide a lancing deviceproviding improved stimulation of sample generation and easiermonitoring of sample size.

[0008] Thus it can be seen that a need exists for an improved lancingdevice and methods for penetrating tissue to facilitate collection of asample of a body fluid. It is to the provision of improved lancingdevices and methods meeting these and other needs that the presentinvention is primarily directed.

SUMMARY OF THE INVENTION

[0009] The present invention comprises improved lancing devices andmethods for penetrating tissue to facilitate collection of a sample of abody fluid. In a preferred aspect, the present invention comprises alancing device for use with a lancet to penetrate tissue and facilitatecollection of a sample of a body fluid. The lancing device preferablyincludes a housing; a lancet carrier translationally mounted to thehousing for carrying a lancet along a stroke traversing an extendedposition wherein a tissue penetrating portion of the lancet extends adistance outwardly of the housing, the lancet carrier comprising a limitmember; and a thumbwheel rotationally mounted to the housing, andcomprising an eccentric contact surface forming a selectively movablestop for contacting the limit member to limit the stroke of the lancetcarrier in the direction of the extended position.

[0010] Accordingly, depth of penetration is easily and accuratelyadjusted to suit the needs of the individual user, and to produce therequired sample size with minimal pain to the user and promote quickhealing. Additionally, by minimizing the size of the wound necessary togenerate a desired sample size, the wound closes quickly after samplingto reduce the incidence of residual bleeding that may stain the user'sclothing.

[0011] The lancing device of the present invention preferably engages astandard lancet, and also provides safe and controlled release of thelancet for disposal. In a preferred aspect, the lancing device of thepresent invention includes a housing, and a lancet carrier mounted tothe housing for releasably engaging a lancet. The lancet carrierpreferably comprises a first gripping jaw; a second gripping jawpositioned in opposition to the first gripping jaw to define alancet-receiving channel between the first and second gripping jaws, thefirst and second gripping jaws being movable between a closed positionfor gripping a lancet and an open position for receiving and releasing alancet; biasing means for biasing the first and second gripping jawstoward the closed position; and a first release arm connected to thefirst gripping jaw and a second release arm connected to the secondgripping jaw, whereby application of force to the first and secondrelease arms moves the first and second gripping jaws toward the openposition.

[0012] In another preferred aspect, the present invention comprises alancing device for use with a lancet to penetrate tissue and facilitatecollection of a sample of a body fluid. The lancing device preferablyincludes a housing having a forward end and a transparent portionadjacent the forward end. The lancing device preferably further includesa lancet carrier mounted to the housing for carrying a lancet between aretracted position within the housing and an extended position wherein atissue penetrating portion of the lancet extends a distance beyond theforward end of the housing. The lancing device preferably furtherincludes a pressure applicator adjacent the forward end of the housing.

[0013] In another preferred aspect, the present invention comprises alancing device for use with a lancet to penetrate tissue and facilitatecollection of a sample of a body fluid. The lancing device preferablyincludes a housing having an overall length, an overall width, and anoverall thickness, the overall length being no more than about fourtimes the overall width, and the overall width being at least about oneand one-half times the overall thickness, wherein the housing isgenerally symmetric about perpendicular first and second planes ofsymmetry, and wherein a trigger button is arranged approximately midwayalong a front face of the housing.

[0014] In another preferred aspect, the present invention is a method ofcollecting a sample of a body fluid. The method preferably comprisesforming an opening in a body tissue at a sample site using a lancingdevice; applying compressive pressure to the sample site with a portionof the lancing device; and observing the sample site through atransparent portion of the lancing device.

[0015] These and other objects, advantages, and features of the presentinvention will become apparent upon reading the following specificationin conjunction with the accompanying drawing figures. The advantages ofthe invention will be realized and attained by means of the elements andcombinations particularly pointed out in the appended claims. It is tobe understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory ofpreferred embodiments of the invention, and are not restrictive of theinvention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a perspective view of a lancing device according to apreferred embodiment of the present invention.

[0017]FIG. 2 is a side view of the lancing device shown in FIG. 1.

[0018]FIG. 3 is a front view of the lancing device shown in FIG. 1.

[0019]FIG. 4 is an exploded view of the lancing device shown in FIG. 1.

[0020]FIG. 5 is a detailed perspective view of a lancet carrier portionof the lancing device shown in FIG. 1.

[0021]FIG. 6 is a perspective view of a stroke-control thumbwheelportion of the lancing device shown in FIG. 1.

[0022]FIG. 7 is a plan view of the stroke-control thumbwheel portionshown in FIG. 6.

[0023]FIG. 8 is a perspective view showing the underside of a housingshell portion of the lancing device shown in FIG. 1.

[0024]FIG. 9 is a perspective view of the lancing device shown in FIG.1, with an endcap portion removed and a lancet installed.

[0025]FIG. 10 is a forward end view of the lancing device shown in FIG.1.

[0026]FIG. 11 is a sectional view of an endcap portion of the lancingdevice shown in FIG. 1.

[0027]FIG. 12 shows a user cocking a lancing device according to apreferred form of the present invention.

[0028]FIG. 13 shows a user lancing a forearm sampling site using alancing device according to a preferred form of the present invention.

[0029]FIG. 14 shows a user lancing a fingertip sampling site using alancing device according to a preferred form of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] Example embodiments of the present invention are described hereinwith reference to the drawing figures. It will be understood that thedescribed embodiments are by way of example only, and are not intendedto be exhaustive or limiting of the scope of the claimed invention. Itwill also be understood that the various features and embodimentsdescribed have individual utility as well as utility in their variouscombinations thereof.

[0031] According to a preferred embodiment, and with particularreference first to FIG. 1, the present invention comprises a lancingdevice 10 for penetrating body tissue of a human or animal subject tofaciliate collection of a sample of a body fluid such as blood orinterstitial fluid. As seen with reference to FIG. 13, the lancingdevice 10 is well suited for use in self-sampling from a forearmsampling site 12 of the subject or, as seen with reference to FIG. 14,from a fingertip sampling site 14 of the subject.

[0032] The lancing device 10 preferably comprises an exterior housing 16having a housing geometry configured for ease of use, even by userssuffering from impaired dexterity or eyesight. As described herein, thehousing 16 includes the overall outer envelope of the lancing device 10and, in an example embodiment described in greater detail below,comprises an endcap and front and back housing shells. The housinggeometry preferably comprises a length L defined between a forward end20 and a rear end 22, a width W defined between a first side 24 and asecond side 26, and a thickness t defined between a front 28 and a back30. In preferred form, the housing 16 is generally symmetric aboutperpendicular first and second central planes of symmetry 32, 34, andthe stroke of a lancet carried by the lancing device 10 extendsgenerally linearly along a central axis defined by the intersection ofthe first and second central planes of symmetry 32, 34. In preferredform, the overall length L is less than four times, and more preferablyless than three times the overall width W. This aspect ratio (i.e., L/W)of no more than 4:1, and more preferably no more than 3:1, provides thelancing device 10 with improved stability in use, which is of particularbenefit in enabling users with impaired dexterity to apply pressurebetween the forward end 20 and a sampling site. According to preferredform, the overall width W of the lancing device 10 is at least 1½ times,and more preferably about twice the overall thickness t. This transverseratio (W/t) of at least 3:2, and more preferably about 2:1, provides aneasy to grip device which resists twisting about the central axis. Asused herein, “overall” dimensions refer to dimensions of the mainportion of the housing, not including any irregular portions such assharp projections or recesses therefrom or therein. The rear end 22preferably comprises a generally flat rear panel without edges or sharpradii, generally perpendicular to the stroke of a lancet carried by thelancing device 10, and preferably has a gradual radius of curvature togenerally conform to the palm, finger or other portion of a human hand.The forward end 20 preferably also comprises a generally flat forwardpanel oriented generally perpendicular to the stroke of a lancet carriedby the lancing device 10. The housing 16 is preferably generallyrectangular, and its major exterior surfaces (e.g., the first and secondsides, the front, the back, and the forward and rear ends) are generallyperpendicular or parallel to the central axis. Edges at theintersections of major surfaces are preferably radiused to providecomfort in use. So configured, a user can easily apply pressuresufficient for sampling, between the forward end 20 and a sampling site,by applying compressive force to the rear end 22 in an axial direction,while maintaining the device in a stable and upright position, as shownfor example in FIG. 13. In this manner, the stroke of the lancet isoriented generally perpendicular to the skin at the sampling site, toprovide a straight in-straight out lancing of the skin for improved usercomfort. According to a presently preferred form, the housing 16 has amaximum overall length of about 100 mm, and is preferably between about40 mm to 100 mm, and more preferably between about 80 mm to 90 mm. Theoverall width is preferably at least about 25 mm, and more preferablybetween about 30 mm to 35 mm, at the widest portion of the housing. Theoverall thickness is preferably between about 10 mm to about 20 mm, andmore preferably between about 15 mm to about 20 mm, at the thickestportion of the housing.

[0033] The lancing device 10 preferably further comprises a lancetcarrier 38 comprising means 40 for releasably engaging a standard lancet42, described with reference to FIGS. 2 and 3. The lancing device 10 canbe adapted for use with any of a number of commercially availablelancets, and the lancets will typically have a needle diameter ofbetween 30 gauge to 21 gauge, and more preferably about 25 gauge,although smaller or larger gauge needles may be suited for particularapplications. The lancet carrier 38 is preferably formed from plastic,metal or other substantially rigid material(s), as by injection molding.In preferred form, the means 40 for releasably engaging a standardlancet 42 comprises a resilient clamp having a first gripping jaw 44 anda second gripping jaw 46 positioned in opposition to the first grippingjaw to define a lancet-receiving channel therebetween. The first andsecond gripping jaws 44, 46 are preferably movable between a closedposition for gripping a lancet 42, and an open position for receivingand releasing the lancet 42 in a controlled manner. The means 40 forreleasably engaging a standard lancet 42 preferably further comprisesbiasing means for biasing the first and second gripping jaws 44, 46toward the closed position. According to a preferred embodiment depictedin the drawing figures, the first and second gripping jaws 44, 46comprise opposed portions of an integrally formed split cylinder, andthe biasing means comprises an intact portion of the cylinder, or anintegrally formed spline 48 connecting the first and second grippingjaws 44, 46. Alternatively, the first and second gripping jaws 44, 46can be separately formed, and the biasing means can comprise interactingportions of one or both jaws, and/or a separate biasing element such asa spring. In order to provide ease of insertion of a lancet 42 betweenthe first and second gripping jaws 44, 46, and controlled release of thelancet therefrom, a first release arm 50 is provided, extending from thefirst gripping jaw 44, and a second release arm 52 is provided,extending from the second gripping jaw 46. The first and second releasearms 50, 52 are preferably integrally formed with the first and secondgripping jaws 44, 46, or alternatively can be separately formed andattached. Outer surface portions of the first and second release arms50, 52 are preferably knurled, grooved, or otherwise textured to form agripping surface. The first and second release arms 50, 52 preferablyextend generally tangentially from the first and second gripping jaws44, 46, opposite the free ends of the gripping jaws and beyond thebiasing means, whereby application of force to the first and secondrelease arms 50, 52 moves the first and second gripping jaws 44, 46toward their open position for easy and controlled insertion and releaseof a lancet 42. The knurled or grooved gripping surfaces allow a user tosqueeze the first and second release arms 50, 52 together, as forexample, between the user's thumb and forefinger, for insertion andremoval of a lancet.

[0034] The lancet carrier 38 is preferably translationally mounted toslide within the housing 16 for carrying a lancet 42 along areciprocating stroke from a retracted position wherein the lancet issubstantially entirely within the housing, through a cocked position, toan extended position wherein at least a tissue-penetrating portion 56 ofthe lancet extends a distance outwardly beyond the housing, and back tothe retracted position. The lancing device 10 preferably furthercomprises a cocking mechanism for shifting the lancet carrier from theretracted position to the cocked position, driving means for driving thelancet 42 from the cocked position to the extended position, andretraction means for returning the lancet carrier from the extendedposition to the retracted position. The driving means for driving thelancet 42 from the cocked position to the extended position preferablycomprises a compression spring 60 engaged between a post 62 extendingfrom a back housing shell 64 and a partition 66 of the lancet carrier38. The compression spring 60 biases the lancet carrier 38 toward itsextended position, and serves to propel the lancet carrier along atissue-penetration portion of its stroke. The lancet carrier 38preferably comprises one or more rails 68 adapted to slide in engagementwith one or more fins 70 formed on the interior face of the back housingshell 64, and the post 62 extends through a slot 72 in the lancetcarrier 38, thereby constraining the lancet carrier to slide generallylinearly parallel to the central axis of the housing 16. The interiorsurface of a front housing shell 74 preferably comprises a channel 76for engaging a cooperating rib 78 of the lancet carrier 38 to guide thelancet carrier 38 along a generally linear stroke. Upon assembly, thefront and back housing shells 74, 64 are coupled, as by crush pins,fasteners, adhesive, or other attachment means, and the lancet carrier38 is preferably constrained therebetween to a well-guided, generallylinear stroke along or adjacent the central axis of the housing 16,whereby the lancet is driven along a straight in-straight out path,penetrating the skin of the sampling site at an angle generallyperpendicular to the skin surface.

[0035] The cocking mechanism arms the lancing device 10 by placing thespring 60 into compression, storing potential energy which is convertedto kinetic energy as the lancet is driven through the tissue-penetratingportion of its stroke. The cocking mechanism is preferably actuated bythe user by grasping a cocking actuator 80 adjacent the rear end 22 andpulling the cocking actuator away from the housing 16, as shown in FIG.11. In a preferred embodiment, the cocking actuator comprises first andsecond halves 80 a, 80 b, that are attached to opposite sides of acocking carriage 82 by pin connections. The cocking carriage 82 slidesbetween opposed partitions 84, 86 of the back housing shell 64, andincludes a pair of shoulders 88, 90 for abutting the ends of thepartitions to limit the traverse of the cocking carriage 82. One or morelips 92 are preferably formed adjacent the rearward end of the lancetcarrier 38, and project over an edge 94 of the cocking carriage 82,whereby retraction of the cocking carriage as shown in FIG. 11 draws thelancet carrier rearward into a cocked position in which the spring 60 iscompressed. As the lancet carrier 38 is drawn into its cocked position,the tip of a cantilevered retaining finger 100 rides over an inclinedramp 102 formed on the interior surface of a front housing shell 74, asshown in FIG. 10. The retaining finger 100 flexes as it passes over theramp 102, and snaps to rest on an upper surface of the ramp to retainthe lancet carrier 38 in its cocked position until released by thetriggering mechanism described below.

[0036] A return spring 106 is preferably coupled between a firstretaining lug 108 on the cocking carriage 82 and a second retaining lug110 on the lancet carrier 38, to draw the cocking actuator 80 backagainst the housing 16 after the lancing device is cocked. The returnspring 106 also serves to retract the lancet carrier from its extendedposition to its retracted position after triggering the device, therebywithdrawing the tissue-penetrating portion 56 from the tissue of thesampling site to minimize any pain experienced by the subject. As willbe understood by those skilled in the art, the compression spring 60 isrelatively stiffer than the return spring 106 so that upon triggeringthe device, the compression spring drives the lancet carrier 38 throughits entire stroke, from the cocked position to the extended position,before the return spring withdraws the lancet carrier. The return spring106 is preferably an expansion spring, rather than a compression spring,whereby the return spring returns the lancet carrier to its retractedposition without significant oscillation. By appropriately balancing thespring 60 and the return spring 106, a smooth and quick stroke of thelancet carrier is achieved, and oscillation of the lancet carrier isminimized to ensure that the used experiences only a single stick by thelancet.

[0037] The lancing device 10 preferably further comprises a triggeringmechanism for releasing the lancet carrier 38 from its cocked position.A trigger button 120 is preferably mounted on the front 28 of thehousing 16, and includes one or more retaining clips 122 and atriggering pin that extends through the front housing shell 74 adjacentthe upper surface of the ramp 102. A large trigger button 120 ispreferably provided for ease of use, and preferably extends acrosssubstantially the entire width of the front face of the housing 16. Forexample, in an embodiment of the device having a housing width of about30 mm, a trigger button 120 about 20 mm wide is provided. The triggerbutton is preferably arranged generally centrally along the front 28 ofthe housing, approximately midway between the forward end 20 and therear end 22, where a user can easily trigger the device while pressingthe forward end of the device against a sampling site. For example, inan embodiment of the device having a housing length of about 87 mm, thetrigger button 120 is located about 40 mm from the forward end 20. Thesize and orientation of the trigger button, in combination with theabove-described transverse ratio of the housing, have been found toprovide superior ergonimics and ease of use, as the trigger button iswithin easy reach of a user's thumb or finger in a variety of grippingpositions. The back 30 opposite the trigger button 120 preferablycomprises a generally broad, flat panel, so that a user can easily andcomfortably grip the device, as between a thumb and forefinger, todepress the trigger button 120 with his/her thumb. The front housingshell 74 preferably includes a trigger recess 124 for receiving thetrigger button 120. A spring 126 is preferably provided to bias thetrigger button 120 outwardly. When the device is cocked and the tip ofthe retaining finger 100 is engaged against the upper surface of theramp 102 to hold the lancet carrier 38 in its cocked position, the tipof the retaining finger presses against the triggering pin. When theuser presses the trigger button 120, the triggering pin disengages theretaining finger from the upper surface of the ramp, releasing thelancet carrier 38, which is then driven by the compression spring 60through the tissue-penetrating portion of its stroke to the extendedposition, whereupon the return spring 106 then retracts the lancetcarrier 38 to its retracted position.

[0038] The lancing device 10 preferably further comprises stroke controlmeans for controlling the stroke range, and thereby controlling thedepth of penetration of the tissue penetration portion 56 of the lancet42 into the body tissue of the sampling site. The stroke control meanspreferably comprises a limit member 140 attached to or comprises aportion of the lancet carrier 38, and a stop 142 attached to the housing16. Contact between the limit member 140 and the stop 142 limits therange of the stroke of the lancet carrier 38 in the forward direction,and defines the extended position of the lancet carrier. In preferredform, the stroke control means is adjustable to permit the user toselectively adjust the stroke range and thereby varying the depth ofpenetration of the tissue penetration portion 56 of the lancet 42 intothe body tissue of the sampling site. In preferred form, a selectivelymovable stop 142 permits the user to adjust the stroke range by varyingthe position at which the limit member 140 contacts the stop 142 to stopthe forward travel of the lancet carrier 38. According to a preferredembodiment understood best with reference to FIGS. 2, 8 and 9, thestroke adjustment means comprises a thumbwheel 144 rotatably mounted tothe housing 16. As used herein, the term “thumbwheel” includes rotatingdials or other elements, translating slide mechanisms, or other movablestop mechanisms, that are manipulable in any way by the user, andspecifically is not limited to elements manipulable by the thumb of auser or by any particular body part of the user. A central opening 146in the thumbwheel 144 preferably receives a split-ring axle 148 on thefront housing shell 74, whereby the axis of rotation of the thumbwheelis not aligned with, and more preferably is generally perpendicular to,the central axis of the housing. Alternatively, a solid ring axle can beprovided. The thumbwheel 144 preferably carries the stop 142, and thestop 142 comprises an eccentric contact surface, whereby rotation of thethumbwheel varies the point of contact by the limit member 140, forwardand rearward in the direction of the central axis of the housing, tolimit the range of the stroke of the lancet carrier 38 in the forwarddirection. For example, as seen in FIG. 9, the stop 142 comprises aneccentric surface that spans an arc α of approximately 30° to 50° alongthe thumbwheel, and is eccentrically offset approximately 2 mm. In thismanner, selective rotation of the thumbwheel 144 by the user through thespan of the arc α a varies the depth of penetration of the tissuepenetration portion 56 of the lancet 42 from a depth of approximately0.025 inch to approximately 0.100 inch. Alternatively, the thumbwheelcan comprise an eccentric surface spanning an arc of less than 30° ormore than 50°. By directly controlling the stroke range, the presentinvention reduces tolerance stacking and provides more consistentcontrol of the penetration depth than some previously known devices thatuse interchangeable or screw-adjusted end caps for control ofpenetration depth. The thumbwheel 144 is preferably mounted generallymidway along the length of the housing 16. A ribbed, knurled, orotherwise textured edge portion 150 of the thumbwheel 144 preferablyprojects from one or both of the first and second sides 24, 26, tofacilitate depth adjustment. A portion of the side(s) of the housing 16may be recessed to permit access to the thumbwheel for adjustment, whileshielding the thumbwheel against inadvertent contact during use of thedevice.

[0039] The lancing device 10 preferably further comprises a depthindicator for indicating the set stroke range and, correspondingly, thedepth of penetration of the tissue penetration portion 56 of the lancet42 into the skin. According to a preferred embodiment, the depthindicator comprises indicia 152 on the thumbwheel 144, and a cooperatingopening or window 154 through the housing for displaying the indicia. Instill further preferred embodiments, the stroke adjustment means of thelancing device 10 further comprises indexing means for allowing the userto increment the forward extent of the stroke range, and accordingly thepenetration depth, through a plurality of discrete positions. Inpreferred form, the indexing means comprises an arcuate series ofdetents 156 on the interior of the front housing shell 74, and one ormore cooperating projections 158 formed on the thumbwheel 144. Rotationof the thumbwheel 144 causes the projection(s) 158 to ride over theseries of detents 156, providing tactile feedback to the user.

[0040] The present invention preferably further comprises a lancingdevice 10 having a pressure applicator for tensioning skin at the samplesite through the application of compressive pressure against the samplesite, and for stimulating the generation of a sample of body fluid of adesired quantity. In preferred form, the pressure applicator portion ofthe lancing device is adjacent or surrounds the path of the tissuepenetrating portion 56 as the lancet traverses its stroke toward theextended position. In this manner, the lancing device need not berepositioned for pressure application after the tissue is pierced. Thepressure applicator preferably comprises a forward panel 170 adjacent orforming the forward end 20 of the housing 16. In preferred form, theforward panel 170 comprises the forward end of an end cap 172 that isreleasably attached to the forward ends of the assembled front and backhousing shells 74, 64. The endcap 172 is shown attached in FIG. 1, anddetached in FIG. 9. The forward panel 170 preferably defines an opening174 therethrough, for allowing passage of at least the tissuepenetrating portion 56 of a lancet 42 towards its extended position. Araised lip 176 preferably projects a distance forward from the forwardpanel, and surrounds at least a portion of the opening 174. In preferredform, the opening 174 is between about 4 mm to 8 mm in diameter. Morepreferably, the opening 174 is less than about 6mm in diameter, so thata standard lancet will not pass therethrough, thereby reducing the riskthat the lancet will be released from containment within the end cap172. An opening diameter of about 6 mm is presently considered toprovide superior sample collection results, while preventing release ofthe lancet. The raised lip 176 preferably comprises an annular ringsurrounding the opening 174, and projects forward from the forward panel170 a distance of between about 1 mm to 3 mm, and most preferably about2 mm. The annular ring preferably presents a generally forward-facingannular land about 2 mm across. The disclosed dimensions of the opening174 and the raised lip 176 have been found to produce surprisinglysuperior results in stimulating sample generation without unduediscomfort or bruising to the subject, and without leaving appreciablecompression marks on the skin surrounding the sampling site, when usedaccording to the sampling procedures herein described. In particular, itis believed that the provision of the generally flat forward panel 170reduces discomfort to the user by distributing compressive pressure overa larger surface area at the sampling site and limiting the extent towhich the raised lip 176 may compress the skin and underlying tissue atthe sampling site. The provision of a raised lip 176 having the stateddimensions, and provided with the above-described annular land, furtherlimits the depth of compression and reduces user discomfort that mightresult from compression with a sharper contact surface.

[0041] The present invention preferably further comprises a lancingdevice 10 having a transparent portion adjacent the forward end 20 topermit the subject to visually observe the size of a drop of blood orother fluid sample being collected. In a preferred embodiment, theentire end cap 172 is formed from a transparent material such as a clearplastic. Alternatively, the transparent portion comprises a wall orwindow of transparent material or a view hole or opening provided in anotherwise translucent or opaque portion of the end cap 172 or otherportion of the housing 16. The transparent portion is positioned topermit observation of the sample site through the opening 174 after thetissue penetrating portion 56 has pierced the tissue of the sample site.The combination of the transparent portion with the adjacent pressureapplicator described above advantageously permits the user to observethe sampling site and monitor the sample size as pressure is applied tostimulate sample generation. In a further preferred embodiment, samplesize indicia 180 are provided adjacent the opening 174, most preferablyon the interior surface of the forward panel 170, to provide a sizereference for comparison with the size of the drop of blood or otherfluid sample being collected. In an example embodiment, the sample sizeindicia 180 is a circular mark having a diameter equal to the diameterof a blood drop of the requisite fluid volume required for analysisusing a standard blood glucose testing system.

[0042] The present invention further comprises a method of collecting asample of a body fluid. The method of the present invention preferablycomprises forming an opening in a body tissue such as skin at a samplesite of the tissue; using a lancing device. In preferred form, thelancing device comprises a lancet having a tissue penetrating portion, apressure applicator, and a transparent portion, substantially asdescribed herein. For example, with reference to the above-describedlancing device 10, the step of forming an opening in a body tissue cancomprise: removing an end cap 172 from the lancing device; loading alancet between the jaws 44,46 of a lancet carrier 38; replacing the endcap; adjusting the stroke control means to the desired depth ofpenetration; cocking the lancing device; pressing the forward panel 170against the forearm, finger or other sampling site; and pressing thetrigger button 120 to release the lancet carrier. The lancet is drivenfrom its cocked position to its extended position, whereupon the tissuepenetrating portion of the lancet forms an opening in the tissue at thesampling site, and then is retracted to its retracted position via thereturn spring 106. The opening 174 and raised lip 176 cooperate totension the skin at the sampling site during and after the penetrationof the tissue. Thus, it may be preferable to apply slight or moderatecompressive pressure to the sampling site with the pressure applicatorprior to the lancet stick, to pre-tension the skin at the sampling siteand cause skin at the sampling site to bulge into the opening 174.Alternatively, the forward end of the device can be placed in lightcontact with the sampling site prior to the lancet stick, and increasedpressure applied after the stick. The method of the present inventionpreferably further comprises applying compressive pressure after thepuncture to the sampling site with a pressure applicator portion of thelancing device to stimulate the flow of a body fluid such as bloodthrough the opening in the tissue at the sampling site. The opening 174and raised lip 176 tension the tissue to open the wound and generate aflow of body fluid. Steady compressive pressure or varying compressivepressure, as by pumping the device against the sampling site, can beapplied. As pressure is applied, the sample site is preferably observedthrough a transparent portion of the lancing device. If a sample sizeindicia is provided, the collected sample of body fluid is monitored incomparison to the sample size indicia. When the collected sample growsto the requisite size, the device is removed from the sample site.Removal of the pressure applied by the device allows the wound to close,facilitating faster clotting and healing, and reducing or eliminatingthe extent of any residual bleeding that could stain the user'sclothing. The collected sample of body fluid is then subjected toanalysis according to any of a variety of analytic techniques.

[0043] While the invention has been disclosed in preferred forms, itwill be apparent to those skilled in the art that many modifications,additions, and deletions may be made therein without departing from thespirit and scope of the invention as set forth in the following claims.

1-30. (Canceled)
 31. A lancing device for use with a lancet to penetratetissue and facilitate collection of a sample of a body fluid, thelancing device comprising: (a) a housing having front and back housingshells; (b) a lancet carrier mounted with the housing for releasablycarrying a lancet having a tissue penetrating portion from a retractedto position to an extended position; (c) a transparent plastic end capremovably and releasably attachable to the housing, the end capcomprising; (i) an opening for allowing passage of the tissuepenetrating portion of the lancet through the cap, the opening having adiameter less than a diameter of the lancet yet greater than a diameterof the tissue penetrating portion; and (ii) a pressure applicatorsurrounding the opening; (d) a cocking actuator operably connected tothe lancet carrier; and (e) a trigger button operably connected to thelancet carrier and to the cocking actuator, the trigger buttonpositioned on the lancing device between the cocking actuator and thetransparent end cap.
 32. The lancing device according to claim 31further comprising stroke control means for controlling the distance thetissue penetrating portion of the lancet extends beyond the opening inthe end cap when the lancet carrier is moved to the extended position,the stroke control means comprising indexing means to provide tactilefeedback.
 33. The lancing device according to claim 32, wherein thestroke control means has at least five positions.
 34. The lancing deviceaccording to claim 31, wherein the pressure applicator comprises araised lip around at least a portion of the opening.
 35. The lancingdevice according to claim 34, wherein the raised lip is an annular ring.36. The lancing device according to claim 34, wherein the raised lip isadjacent the opening.
 37. The lancing device according to claim 34,wherein the raised lip projects 1 mm to 3 mm.
 38. The lancing deviceaccording to claim 31, wherein the pressure applicator comprises aforward-facing annular land surrounding the opening.
 39. The lancingdevice according to claim 38, wherein the forward-facing annular land isabout 2 mm across.
 40. The lancing device according to claim 31, whereinthe opening has a diameter of 4 mm to 8 mm.
 41. A method of collecting abody fluid sample, the method comprising: (a) positioning a lancingdevice on a desired sample site, the lancing device comprising: (i) ahousing having front and back housing shells; (ii) a lancet carriermounted with the housing for releasably carrying a lancet having atissue penetrating portion from a retracted to position to an extendedposition; (iii) a transparent plastic end cap removably and releasablyattachable to the housing, the end cap comprising; (A) an opening forallowing passage of the tissue penetrating portion of the lancet throughthe cap, the opening having a diameter less than a diameter of thelancet yet greater than a diameter of the tissue penetrating portion;and (B) a pressure applicator surrounding the opening; (iv) a cockingactuator operably connected to the lancet carrier; and (v) a triggerbutton operably connected to the lancet carrier and to the cockingactuator, the trigger button positioned on the lancing device betweenthe cocking actuator and the transparent end cap; (b) actuating thecocking actuator; (c) pressing the pressure applicator against thesample site; (d) pressing the trigger button to release the lancet sothat the tissue penetrating portion penetrates the sample site; and (e)monitoring the sample site through the transparent end cap. 42.(Canceled)
 43. The method according to claim 41, wherein the step ofpressing the pressure applicator against the sample site comprises: (a)applying compressive pressure to the sample site.
 44. The methodaccording to claim 43, wherein the step of applying compressive pressureto the sample site comprises: (a) applying steady compressive pressureto the sample site.
 45. The method according to claim 43, wherein thestep of applying compressive pressure to the sample site comprises: (a)applying varying compressive pressure to the sample site.